Vernier rheostat



Feb.14, 192 8. f 1,658,866

- c. H. THORDARSON VERBIER RHBOSTAT Filed May 22. 1922 Patented Feb. 14,1928.

UNITED- STATES CHESTER H. THORDARSON, OF CHICAGO, ILLINOIS.

VERNIER RHEOS'IAT.

Application filed May 22,

This invention relates to improvements in rheostats for regulating oradjusting an electrical circuit, and refers more particularly to a novelvernier' rheostat, the circuit of which composes a main winding,constituting almost the entire rheostat circuit, and a short orfractional part compris ng, 1n length, a short subdivision of saidentire circuit and which is in circuit with said winding and bindingposts for connection to an external circuit, and containing also a mainsliding element which travels over and in contact with the main windingor its contacts and a secondary sliding element whichtravels'independently of the main sliding element over the fractionalcircuit part, whereby the latter element or member is capable of cuttingin or out fractional portions between one or more coils or contacts ofthe main winding so as to thereby attain very minute subdivisions of therheostat circuit.

An object of the invention is to provide an exceedingly simple andeflicient rheostat of this character, in which the parts may beeconomically made and economically assembled, and also to provide aconstruction in which the fractional portion of the circuit is wellinsulated from the main winding of the rheostat circuit.

A further object of the invention is to produce a construction ofrheostat in Which the operative parts are compactly arranged andprotected by the general construction of the device from exteriorbruises.

The construction herein shown is particu-' larly well adapted for use inthe tuning circuits of radio transmitting and receiving sets but may beadapted to other uses where fine graduations of current flow through acircuit is required.

The invention consists in. the combination and arrangement of the partsshown in the drawings and described in the specification, and is pointedout in the appended claims.

In the drawings:

Figure 1 is an end view of a rheostat embodying my invention.

Figure 2 is an axial section thereof, with parts shown in elevation.

Figure 3 is a diagram of the rheostat circuit.

Figure 4 is a modified diagram of the rheostat circuit.

Referring first to Figure 3, 10 designates a winding constituting theprincipal part of 1922. Serial No. 562,607.

the rheostat circuit. 11 designates a fractional part of said circuitwhich, in practice, is made of a lengthof approximately that of one ortwo of the coils of the winding. 12 designates a conducting arm which isadapted to travel along the length of and in contact with the winding10, and 13 designates a like (conducting arm which is adapted to travelalong and in contact with the fractional circuit part. Said arms areshown in Figure 4 electrically connected, as at the point 14. 15, 16designate binding posts by which the rheostat circuit is connected tothe wires of an external circuit. The said.

arms 12, 13 are, in the mechanical construction, mounted to rotate onthe same axis, and each of said arms is adapted to be independentlymovable so that, with the arm 12 on one of the coils or contacts of thewinding, the other arm 13 can be moved along the fractional circuit part11, so as to divide the current force into as many in crements as thelength of said fractional conductor bears ratio to the length of thecoil or coils with which the arm 12 is in contact.

Referring now to the illustrated mechanical construction constitutingone embodiment of my invention, 17 designates a metal base plate. It isprovided with a rim 18 which is made of one piece of metal that iscurved to form an almost complete circular element that may be fixed tothe plate 17, as by means of an integral spur or flange 20 struck upfrom said base plate and riveted to the ends of the rim member. The saidrim is shown as made of thin gauge metal and is of a width to form aprotecting wall for parts enclosed therein, as will hereinafter bedescribed.

The said rim also forms a core or support for the winding 10 of therheostat circuit, said winding being Wound in elongated coils about thesaid rim throughout the principal portion of its circumferential length.The Winding is insulated from the metal of the rim by an insulating tube21 made to fit closely about the portions of the rim at the sides of theflange or spur 20 and directly supports the winding 10.

22 designates a disc made of insulating material which is seated on thebase 17 and is enclosed by the rim 18 and its winding 10. Saidinsulating disc 22 at its base is made the full diameter of the rim, andis formed at said base with a radial extension or flange 24 that extendsbeneath the winding to insulate the winding from the base 17. The disc22 is provided near its edge remote from the flange 24 with an externalannular groove 25 in which is seated the fractional portion 11 of therheostat circuit,

. said fractional circuit part being a plain curved wire. tion isconnected at one end to the binding post 15 and is laid between its endsin said external groove 25 and is open at its other end. The 'coil 12 isconnected at ome end with the binding post 16 and is open at its otherend, the fractional circuit part and winding being thus in seriesthrough the arms 12 and 13. Said disc 22 is provided exterior to saidgroove 25 with an annular recess or groove 26 of some depth, and thelatter groove is flanked by an annular en closing flange 27 of lessheight than the thickness of said disc. I

28 designates a hollow operating shaft which extends through mountingboard B, in which the shaft is rotatively mounted. Said shaft is reducedat its inner end and is rotatively mounted in a sleeve 28 which extendsthrough the base plate. Said shaft extends beyond-the disc 22 andcarries at its outer end the angularly adjustable conducting arm 13which extends radially from the shaft. Said arm 13 is provided at itsfree end with a down-turned contact finger 30 for engagement with thefractional circuit part 11. Said contact finger 30 also travels in thegroove 26 to hold it engaged with the fractional circuit part 11 andalso to prevent contact of said downturned finger with the winding 10.Said hollow shaft isprovided with a hand wheel 31 by which to rotateit-and the conducting arm 13.

32 designates a second shaft which extends through and is mounted torotate in the shaft 28. Said second shaft extends outwardly beyond thehollow shaft28 and is provided beyond the hand wheel 31 of the shaft 28with an independently'actuable hand wheel 33. The shaft 32 also extendsat its inner end beyond the shaft 28 and carries at its inner end thecontact arm 12 which is disposed radially to the shaft and is adaptedfor contact at its outer end with the coils of the windinglO.

As herein shown, the conducting arm 13 is fixed to a reduced, threadedportion of the shaft 28 by being provided with an enlarged perforatedhead for the passage of said reduced end, and the said head is clampedbetween a solid washer 34 and a nut 35 threaded to saidshaft. The Washer34: is forced by the nut 35 against a split or spring washer 36, whichlatter yieldingly bears on the inner end of a flanged sleeve 28', whichsurrounds the shaft 28 at the disc and constitutes a bearing sleeve forthe Said fractional circuit porlatter shaft. The said conducting arm 12,is likewise provided with a perforated head through which the threaded,reduced, inner end of the shaft 32 extends, and said arm is held fixedlyon said" shaft between lower and upper nuts 38, 39. The metal to metalcontact of the mounting of the conducting arms 12 and 13 and theirfastening nuts and bearing of the shaft '32 in the hollow shaft 28.Thus, with the outer end of the conduct ing arm 12 in contact with oneor more of the coils of the windinglO, the conducting arm 13 can heangularly adjusted on the fractional circuit part 11, so as tofurthersubdivide. the current passing through the rheostat, due to the lengthof said fractional circuit part relatively to the length of the coil orcoils of the winding with which the conducting arm 12 is in closedcircuit.

The said base plate 17 maybe attached to the inner face of a mountingboard B which, in practice, may be a wall of-a cabinet or like structurein which the electrical apparatus to beregulated by the rheostat iscontained. The fastening of the plate 17 may be effected by means ofscrews 22' extending through said plate and the conducting disc intosaid wall. The hand piece .31 of the outer or tubular shaft 28 is spacedfrom said mounting board a distance to permit it to be readilygrasped toturn the same and the conducting arm actuated thereby, and the handpiece of the shaft 32 is spaced from the hand piece 31 to afford freeaccess thereto without disturbing the latter hand piece. t

An advantage of .the construction shown is" that the winding 10 and thefractional portion 11 of the circuit are arranged con The conductingelements of the rheostat,

embracing the winding 10, the fractional circuit part 11, the wipingconducting arms 12 and 13 and their mounting, as well also as theinsulating disc 22, and the rim 18. are made of materials which are notafiected by heat developed in the circuit conductors, so that thereby,after the parts have been assembled and adjusted, the accuracy of the onsaid rim at one end of the winding 10 to prevent contact of theconducting arm 12 with one of the binding posts. A like stop may beprovided on the disc to limit angular movement of the other conductingarm 13.

In Figure 4 is shown a modified wiring diagram, wherein the winding 10'and short circuit part 11 are in direct series and connected to bindingposts 15, 16, and wherein the arms 12, 13'.are not directly in serieswith the coils and circuit part and are represented as electricallyconnectedhy the Wire 14. i a

I claim as my invention:

A Vernier rheostat comprising a base, a rim outstanding therefrom andfixed thereto, an insulating body within said rim,

formed on its circumference with a groove and radially beyond saidgroove with a guard flange, a conductor embracing a winding on andinsulated from said rim, and a fractional circuit part fitted in saidbody groove, and electrically connected conducting arms mounted forseparate angular adjustment about an axis concentric to said rim,adapted for wiping contact, one with said winding, and the otherprovided with an inturned finger lying outside said body periphery forwiping contact with said fractional circuit part, and lying within saidguard flange.

In witness whereof I claim the foregoing as my invention, I hereuntoappend my sig= nature this 17 day of May, 1922.

CHESTER H. THORDARSON.

